This invention relates to the generation of electricity by the isentropic expansion of high-pressure fuel gas and steam. More particularly, the invention involves expansion of the fuel gas admixed with steam in a steam turbine to drive an electric generator, the steam being produced by burning the expanded fuel gas, preferably in a manner that yields minimal air pollution.
Processes for generating electricity by the combustion of high-pressure fuel gas are unable to meet the increasingly lower limits imposed by government regulations on the air pollutants: nitrogen oxides (NO.sub.x), carbon monoxide (CO) and unburned hydrocarbons (UHC), that are discharged into the atmosphere with the combustion product gases. Such processes frequently are made to comply with the regulations by passing the combustion product gases through a treatment plant that removes the pollutants before the gases are vented. Other such processes employ catalysts or unusual combustion conditions to suppress the formation of pollutants. All the remedial techniques increase the cost of generating electricity.
Currently popular schemes for generating electricity by the combustion of high-pressure fuel gas are based on the use of gas turbines which have gaseous effluents with high contents of NO.sub.x, CO and UHC. Various efforts are being made to find ways to bring the operation of gas turbines into compliance with environmental regulations.
However, a principal object of this invention is to avoid the use of gas turbines in the generation of electricity by substituting steam turbines therefor.
A related principal object is to eliminate the use and cost of a turbo-expander to expand high-pressure fuel gas by mixing the gas with steam that is passed through a steam turbine.
A further object is to carry out the combustion of the expanded fuel gas to produce the steam passed through the turbine, by passage through a porous fiber burner and effecting flameless combustion on the exposed surface of the burner to minimize the formation of NO.sub.x, CO and UHC.
These and other features and advantages of the invention will be evident from the description which follows.